Apparatus and method for determining feedscrew and barrel wear

ABSTRACT

An apparatus and a method for determining wear of a feedscrew and barrel combination includes measuring wear of the barrel using a gage plug in a measuring aperture in the barrel or an ultrasonic thickness gauge and measuring feedscrew wear with an eddy current sensor or a dial indicator mounted in the measuring aperture. A system gathers wear data from various production installations, analyzes the data to predict remaining life of the barrel and the feedscrew and generates an order for replacement parts to be manufactured and shipped just prior to the end of the remaining life.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of the co-pending U.S. patentapplication Ser. No. 10/965,649 filed Oct. 14, 2004.

This application claims the benefit of U.S. provisional patentapplication Ser. No. 60/643,256 filed Jan. 12, 2005.

BACKGROUND OF THE INVENTION

The present invention relates generally to an apparatus and method fordetecting wear in a material processing machine and, in particular, toan apparatus and method for determining the wear of feedscrew flightsand adjacent barrel interior surfaces.

Typically, a barrel and feedscrew are used to mix and melt variousmaterials used in extrusion, blowmolding and injection processes. Forexample, bulk plastic material is fed into an extruder, an injectionmolding machine or a blow molder through the barrel or cylinderutilizing a rotating helical screw. Such a machine is operated at anelevated temperature and if it is required to be shut down, the plasticmaterial tends to solidify. Many plastic materials are highly abrasiveand tend to wear the flights on the screw thereby widening the gapbetween the outer edge of the flights and the inner surface of thebarrel or cylinder. Such a condition will tend to prevent the uniformfree flow of material through the barrel thereby causing problems in theconsistency of the plastic material. Other problems that can occur aregalling in the barrel through adhesive wear or metal to metal contactand misalignment of the screw through excessive shear or deflection ofthe screw mechanism.

Previously, the only way to check the dimensional clearances in such amechanism was to shut it down and remove the screw from the barrel.Since the plastic material would solidify, the screw and the barrelwould have to be cleaned and the dimensions checked utilizing mechanicalmeasuring devices. Then, the mechanism would have to be reassembled.Such a procedure tended to result in lost production time and did notcompletely eliminate the occasional breakdowns between regularmeasurements.

In U.S. Pat. No. 4,604,251, there is shown an apparatus and method forchecking the dimensional relationship between the screw flights and theinner diameter of a barrel or cylinder during the operation of theplastic material feed device. Utilizing the Foucault current or eddymethod of detection, a probe is located in an aperture formed in theside of the barrel or cylinder. The end of the probe is positioned nearthe inner surface of the barrel or cylinder. The probe generates anelectrical signal having a magnitude proportional to the distancebetween the outer edge of the flight on the screw and a sensing coillocated in the probe. The probe output signal is sensed and converted toa digital distance display for use by the machine operator.

The magnitude of the signal can be scaled to generate a display numberrepresenting the actual measurement between the edge of the flight screwand the inside of the barrel or cylinder in English or metric units. Thesignal can be stored, selectively reset and two or more probe detectionsignals can be selectively displayed.

SUMMARY OF THE INVENTION

The present invention concerns an apparatus for determining wear of afeedscrew and barrel combination comprising: a barrel having a centralbore extending along a longitudinal axis and a measuring aperture formedin a wall of the barrel, the measuring aperture extending along an axisradially from the longitudinal axis; a feedscrew rotatably positioned inthe central bore; and a gage plug releasably retained in the measuringaperture, the gage plug having an inner end curved to correspond to acurvature of a surface of the central bore surrounding an inner end ofthe measuring aperture. The apparatus includes locating means formaintaining alignment of the gage plug inner end with the central boresurface during rotation of the feedscrew in the barrel. A retaining plugis releasably retained in the measuring aperture and prevents removal ofthe gage plug. The gage plug can have a cap at the inner end formed of amaterial having a wear rate corresponding to a wear rate of the centralbore surface.

A method of determining wear of a feedscrew and barrel combinationaccording to the present invention comprises the steps of: a) forming ameasuring aperture in a barrel with a feedscrew rotatable in a centralbore between an outer surface of the barrel and an inner surface at thecentral bore; b) providing a gage plug having an inner end with acurvature corresponding to a curvature of the inner surface of thebarrel; c) inserting the gage plug in the measuring aperture andaligning the curvature of the inner end with the curvature of the innersurface; d) rotating the feedscrew and then stopping the rotation of thefeedscrew; e) removing the gage plug from the measuring aperture; and f)determining a value of wear in the central bore of the barrel bydetermining a value of wear at the inner end of the gage plug. Themethod further includes a step of inserting a mechanical probe in themeasuring aperture after performing step e) to determine a value of wearof a flight of the feedscrew.

The present invention also concerns an apparatus for determining wear ofa feedscrew and barrel combination comprising: a barrel having a centralbore extending along a longitudinal axis and a measuring aperture formedin a wall of said barrel, said measuring aperture extending along anaxis radially from said longitudinal axis; a feedscrew rotatablypositioned in said central bore; a gage plug releasably retained in saidmeasuring aperture, said gage plug having an inner end curved tocorrespond to a curvature of a surface of said central bore surroundingan inner end of said measuring aperture; and measuring means fordetermining barrel wear at said gage plug inner end when said gage plugis removed from said measuring aperture and for determining wear of saidfeedscrew upon being inserted into said measuring aperture. Themeasuring means can include a dial indicator and a fixture, said fixtureholding said gage plug and said dial indicator in a predeterminedrelationship for measuring said barrel wear. A calibration standard canbe used with said fixture to “zero” said dial indicator. The measuringmeans can include an adapter received in said measuring aperture formeasuring said wear of said feedscrew with said dial indicator. Anextension can be attached to said dial indicator and extend through saidadapter.

An extractor kit can be used for removing said gage plug from saidmeasuring aperture. The extractor kit includes an externally threadedextractor rod having a threaded aperture for threadably engaging saidgage plug, an extractor V-block for contacting an external surface ofsaid barrel, said extractor rod passing through said V-block, and anextractor nut threadably engaging said extractor rod whereby rotation ofsaid extractor nut pulls said extractor rod and said gage plug from saidmeasuring aperture.

The apparatus can include an axially extending dowel attached to saidbarrel wall in said measuring aperture and wherein said gage plug has agroove formed therein, said groove cooperating with said dowel to orientsaid gage plug in said measuring aperture.

The present invention concerns a method for monitoring wear of afeedscrew and barrel combination in a production installation comprisingthe steps of:

a. providing a measuring aperture in a wall of a barrel having a centralbore extending along a longitudinal axis, the measuring apertureextending along an axis radially from the longitudinal axis;

b. positioning a feedscrew rotatably in the central bore;

c. installing a plug releasably retained in the measuring aperture, theplug having an inner end curved to correspond to a curvature of asurface of the central bore surrounding an inner end of the measuringaperture;

d. measuring barrel wear with at least one of the plug and a firstmeasuring device; and

e. measuring feedscrew wear with at least one of the plug and a secondmeasuring device.

The plug can be a gage plug, the first measuring device can include adial indicator and a fixture and said step d. is performed by mountingthe gage plug and the dial indicator in the fixture. The first measuringdevice can include an ultrasonic thickness gauge and said step d. isperformed by using the ultrasonic thickness gauge at an external surfaceof the barrel. The second measuring device can include a dial indicatorand said step e. is performed by removing the plug and mounting the dialindicator in the measuring aperture. The plug can be an eddy currentsensor, the second measuring device can include a detection signalcircuit and said step e. is performed by rotating the feedscrew.

The present invention concerns a method for monitoring wear of afeedscrew and barrel combination in a production installation comprisingthe steps of:

a. measuring at least one of barrel wear and feedscrew wear;

b. generating wear data from the measured wear;

c. transmitting the wear data to a remote location;

d. analyzing the wear data at the remote location; and

e. predicting a remaining life of a one of the barrel and the feedscrewbased at least partially upon the analyzed wear data.

The method can include a step of generating an order for the manufactureand shipment to the production installation of the one of the barrel andthe feedscrew to coincide with an end of the predicted remaining life.The method can include performing said step c. by transmitting at leastone of a material being processed, a speed of rotation of the feedscrewand an operating temperate of the barrel. The method can includetransmitting the analyzed wear data from the remote location to theproduction installation. The method can include performing said steps a.through e. for at least two physically separated productioninstallations.

DESCRIPTION OF THE DRAWINGS

The above, as well as other advantages of the present invention, willbecome readily apparent to those skilled in the art from the followingdetailed description of a preferred embodiment when considered in thelight of the accompanying drawings in which:

FIG. 1 is a schematic representation of a prior art apparatus formeasuring displacement of a feedscrew;

FIG. 2 is a plan view of the prior art probe shown in FIG. 1;

FIG. 3 is a fragmentary plan view taken as if in partial cross sectionthrough the screw and the barrel of FIGS. 1 and 2 showing an apertureformed to accept the probe;

FIG. 4 is a fragmentary plan view of a barrel and feedscrew illustratinga measuring aperture formed in the barrel wall in accordance with thepresent invention;

FIG. 5 is an enlarged cross-sectional view taken along the line 5—5 inFIG. 4 showing a probe for insertion into the measuring aperture;

FIG. 6 is a view similar to FIG. 5 with the feedscrew removed andshowing a gage plug and a retainer plug in accordance with the presentinvention for insertion into the measuring aperture;

FIG. 7 is a top plan view of the retainer plug shown in FIG. 6;

FIG. 8 is a flow diagram of a method for determining barrel wall wearaccording to the present invention;

FIG. 9 is a plan view of a test bar according to the present invention;

FIG. 10A is an elevation view and FIG. 10B is a top plan view of analternate embodiment gage plug according to the present invention;

FIG. 11A is an elevation view and FIG. 11B is a top plan view of analternate embodiment retaining plug according to the present invention;

FIG. 12A is a cross-sectional view and FIG. 12B is a top plan viewshowing the gage plug of FIGS. 10A and 10B and the retaining plug ofFIGS. 11A and 11B installed in a feedscrew barrel;

FIGS. 13A–G include cross-sectional, plan and elevation views of analternate embodiment mechanical version of the wear detector accordingto the present invention;

FIGS. 14A–E show an alternate embodiment gage plug, retaining plug andextraction kit according to the present invention; and

FIG. 15 is a block diagram of a system for performing a method accordingto the present invention for monitoring and maintaining productioninstallations.

DESCRIPTION OF THE PREFERRED EMBODIMENT

U.S. provisional patent application Ser. No. 60/643,256 filed Jan. 12,2005 is hereby incorporated herein by reference.

There is shown in FIG. 1 a schematic block diagram of a prior artapparatus for detecting feedscrew wear or misalignment according asshown in the U.S. Pat. No. 4,604,251, which patent is incorporatedherein by reference. A feedscrew 11 rotates about a longitudinal axis 12thereof. The feedscrew 11 is formed of a generally cylindrical body 13having a helical flight or thread 14 formed on an exterior surface ofthe body 13. A probe 15 is positioned adjacent the flight 14 to sensethe distance between an end of the probe and an outer edge of theflight. The probe 15 generates a detection signal along a cable 16 to adetection signal circuit 17. The magnitude of the output signalgenerated by the detection signal circuit 17 on a line 18 isproportional to the distance between the end of the probe 15 and theouter edge of the flight 14.

The output signal on the line 18 is an input to a switching circuit 19.The switching circuit 19 incorporates a conventional signal holdingcircuit, which stores the magnitude of the signal on the line 18 at thetime a reset switch 20 is closed. This stored signal is generated on aline 21 to a display circuit 22 whereby an indication of the distancebetween the probe and the flight is displayed as a number in a selectedmode of measurement. Various conventional digital or analog displayscould be utilized for the display 22, but a digital display in Englishor metric units is preferred. The probe 15, the circuits 17 and 19 andthe display 22 are provided with electrical power by a power supply 23on a line 24.

The probe 15 of FIG. 1 is shown in plan view in FIG. 2. The probe 15 hasa generally cylindrical body with an externally threaded central portion31. At one end of the probe 15 is a relatively short, narrower diameterportion 32 connecting the body portion 31 to a squared off head portion33. The head portion 33 is adapted to be gripped by an open end oradjustable wrench, or similar tool for threading the body 31 into athreaded aperture in a wall of a barrel or cylinder 34. A nut 35 isthreaded onto the body portion 31 and is utilized as a stop nut againstan outer surface of the barrel 34 (not shown) or a spacer (not shown)positioned between the nut 35 and the outer surface of the barrel 34.

A sensor assembly 36 is positioned at an end of the probe body 31opposite the head portion 33 and includes a wire coil (not shown)connected to the cable 16. The probe 15 has a bore (not shown) formedtherein coextensive with the longitudinal axis of the body 31 to permitthe connection of the coil with the cable 16.

There is shown in FIG. 3 a plan view of an extruder barrel and screwtaken as if in partial cross-section. An aperture 41 is formed in thewall of the barrel 34 extending from an outer surface 42 to an innersurface 43 adjacent an outer edge of the flight 14 on the screw 11. Theaperture 41 is formed with a larger diameter area 44, which is threadedits entire length as shown at 45, that terminates in a step surface 46.The aperture 41 then extends as a narrower diameter portion 47 from thestep surface 46 to the inner surface 43 of the barrel 34 through aninner liner 48 of the barrel. The distance between the sensor assembly36 shown in FIG. 2 and the outer surface of the flight of the screw isapproximately 0.035 inch to 0.040 inch.

As the probe 15 is threaded into the aperture 41, the one end of thethreaded section 31 comes into contact with the step surface 46 whichfunctions as a stop to position the probe with the sensing end 36 in theproper position for sensing the distance between the probe end and theouter edge of the flight 14. When data retrieval is completed, the probe15 is removed from the aperture 14. Typically, the probe 15 is removedand the aperture sealed during regular manufacturing operations toprevent material leakage or damage to the probe 15. A plug (not shown)may be used to seal the aperture 41 when the probe is not in use andremoved.

FIGS. 4–8 show the apparatus and method for detecting wear according tothe present invention. Components shown in FIGS. 4–8 that are similar tothe components shown in FIGS. 1–3 are identified by the same referencenumeral with “100” added. Thus, the feedscrew 11 shown in FIG. 1corresponds to a feedscrew 111 shown in FIG. 4.

FIG. 4 is a fragmentary plan view of a barrel 134 and the feedscrew 111with which the apparatus and method for detecting wear according to thepresent invention can be used. The feedscrew 111 extends along alongitudinal axis 112 as a cylindrical body 113 with a helical flight114 formed on an exterior thereof. The barrel 134 also extends along theaxis 112 and has a central bore 50 in which the feedscrew 111 ispositioned for rotation. A wall of the central bore 50 can be covered bya liner or coating 148 used to reduce wear caused by the materialpassing through the barrel 134. Typically, the liner or coating 148 isformed of a material that is more abrasion resistant than the materialfrom which the barrel 134 is formed. The feedscrew 111 and the barrel134 are of conventional construction and are available from Glycon ofTecumseh, Mich.

The apparatus and method according to the present invention involvesforming a measuring aperture 141 through the wall of the barrel 134 andthe liner or coating 148. The aperture 141 extends radially relative tothe axis 112 from an outer surface 142 of the barrel 134 to an innersurface of the liner or coating 148 as shown in FIGS. 4–6. Extendinginwardly from the outer surface 142, the aperture 141 has a largerdiameter portion 144 that is at least partially threaded 145. Extendingoutwardly from the inner surface 143, the aperture 141 has a smallerdiameter portion 147 that joins the larger diameter portion 144 at astep 146.

As shown in FIG. 5, a probe 115 is configured for insertion into theaperture 141. The probe includes a sensor 136 at one end and a cable 116to carry power to and signals from the sensor 136. A shoulder 1 isformed on the probe 115 for engaging the step surface 146 therebyspacing the sensor 136 a predetermined distance from the axis 112 eachtime the probe is inserted into the aperture 141. The probe 115 can useany known type of proximity detection technology. The detection signalgenerated by the probe 115 can be input to a signal processing anddisplay unit, such as a Hocking “Locator 2” handheld eddy currentinspection unit or a Hocking “Phasec 2” eddy current inspection unit,both available from GE Inspection Technologies, LP of Lewistown, Pa.

As best seen in FIG. 6, the smaller diameter portion 147 is formed inthree sections 52, 53 and 54. The outer section 52 extends inwardly fromthe step surface 146 and is cylindrical. The intermediate section 53tapers from a larger diameter of the outer section 52 to a smallerdiameter of the inner Section 54. The inner section 54 is cylindricaland opens through the liner or coating 148 to the barrel central bore50. A locator recess 55 is formed in the step surface 146 and extendsgenerally parallel to an aids 56 of the aperture that intersects thelongitudinal axis 112 of the barrel 134.

When the probe 115 is not positioned in the aperture 141 for measuringwear on the flight 114 of the feedscrew 111, the aperture is closed by abarrel wear detector, in the form of a gage plug 57, and a retainer orretaining plug 58. The gage plug 57 has a cylindrical body 59 with arecess 60 formed in an outer end surface for receiving a tool (notshown) to aid in positioning the gage plug 57 in the aperture 141. Aninner end surface of the body forms a shoulder 61 from which a pin 62extends. The pin 62 is spaced from the central axis of the body so as tobe received in the recess 55 and a tool in the recess 60 can be used torotate the gage plug 57 to align the pin 62 with the recess 55.Extending axially inwardly from the body 59 is a plug outer section 63corresponding to the aperture outer section, a plug intermediate section64 corresponding to the aperture intermediate section 53 and a pluginner section 65 corresponding to the aperture inner section 54. Aninwardly facing end 66 of the inner section 65 is curved to correspondto the curvature of the inner surface of the barrel 134 and includes acap 67 formed of the same material as the liner or coating 148. Thedistance from the shoulder 61 to the end 66 is the same as the distancefrom the step surface 146 to the inner surface of the liner or coating148. The recess 55 cooperates with the pin 62 to align the curvature ofthe cap 67 with the curvature of the inner surface 143 so that the cap67 will wear at the same rate as the liner or coating 148. Therefore,the length of the gage plug 57 provides an indication of the wear on theinner surface 143 of the barrel 134. However, means for aligning otherthan the recess 55 and the pin 62 can be used.

The gage plug 57 is held in the aperture 141 by the retaining plug 58.As shown in FIGS. 6 and 7, the retaining plug 58 has a cylindrical body68 that is externally threaded 69. The body 68 has a recess 70 formed inan outer end for receiving a tool (not shown) for rotating the threads69 into engagement with the threads 145 in the aperture 141. Theretaining plug 58 is rotated into contact with the gage plug 57 to seatthe plug intermediate section 64 against the aperture intermediatesection 53 and securely close the aperture 141.

As stated above, to assure that the gage plug 57 wears equally anduniformly to that of the inner surface 143 of the barrel 134, the gageplug 57 is produced using the same material layered composition as thewall of the barrel 134. For example, a typical barrel is produced fromtwo different materials to form a bimetallic cylinder. An outer cylinderis typically manufactured from a common mill metal, such as a suitablesteel. The liner or coating 148 is commonly formed from an alloy that isproduced by a spin cast operation to form a cast liner (i.e., innersurface lining). The typical liner 148 has a wall thickness at least0.050 inches thick. The liner 148 is manufactured for high-performanceoperations. Various alloys, such as those available from bimetalliccylinder manufacturer Wexco Corporation of Lynchburg, Va., can be usedfor effectively operating under special environmental conditions such asabrasive and/or corrosive environments. Furthermore, different liningthicknesses can be used for specific applications to increase longevityof the barrel 134. The outer cylinder and the liner are adheredutilizing a fusing process. Alternatively, other types of adjoiningprocesses may be used.

To maintain the same wear rate as the liner 148 of the barrel 134, thegage plug 57 can be manufactured using the same material and thicknessfor the cap 67. However, the cap 67 could be formed of a differentmaterial and thickness that will result in the same wearcharacteristics. Also, the cap 67 could be eliminated and the entiregage plug 57 could be formed of the same or a different material.

FIG. 8 illustrates a method according to the present invention fordetermining the wear of the wall of the barrel 134 without having todisassemble the barrel. As shown in FIGS. 4–6, first the measuringaperture 141 with the recess 55 is formed in the wall of the barrel 134and the gage plug 57 and the retaining plug 58 are provided. In a step80, the gage plug pin 62 is aligned with the locator recess 55. The gageplug 57 is orientated so as to align the curvature of the cap 67 withthe curvature of the liner 148. In a step 81, gage plug 57 is insertedinto the aperture 141 while maintaining an alignment between the locatorpin 62 and the locator recess 55. If the locator pin 62 does not seatwithin the locator recess 55, the gage plug 57 is rotated until thelocator pin 62 is fully seated. The steps 80 and 81 can be combined byinserting the gage plug 57 in the aperture 141 and rotating, ifnecessary, to seat the pin 62 in the recess 55.

In a step 82, the retaining plug 58 is inserted into the aperture 141thereby retaining the gage plug 57. In the preferred embodiment, thethreads 69 on the retainer plug engage the threads 145 on the wall ofthe aperture 141 and the retaining plug 58 is rotated into place. Othermethods of retention may be used, such as a keyed lock-down feature. Ina step 83, the machine including the feedscrew 111 and the barrel 134 iscycled to perform manufacturing operations. At predetermined inspectionintervals or any other time period, the manufacturing operation isstopped to inspect the barrel in a step 84. The retainer plug 58 isdisengaged and removed from the aperture 141 in a step 85. In a step 86,the gage plug 57 is removed from the aperture 141.

In a step 87, the axial thickness of the gage plug 57 is measured. Inthe preferred embodiment, micrometers are used to measure the gage plug,however, any suitable measuring device may be used to measure andinspect the wear of the gage plug 57. In other preferred embodiments,measurements other than the axial thickness or other types ofmeasurement characteristics may be used in determining the wearcharacteristics of the gage plug 57. In a step 88, a determination ismade whether the gage plug 57 has reached or exceeded a wear limit. If adetermination is made in the step 88 that the gage plug 57 has notreached or exceeded the wear limit, then a branch is made at “No” and areturn is made to the step 80 to re-insert the gage plug 57 into thebarrel wall aperture 141. If a determination is made that the gage plug57 is at or has exceeded the wear limit, then the barrel 134 is removedand replaced in a step 89. In a step 90, the gage plug 57 is replacedwith a new gage plug and a return is made to the step 80 to insert thenew gage plug in the new barrel.

The apparatus and the method according to the present invention providean accurate indication of feedscrew wear, barrel wear and/ormisalignment between the feedscrew and the barrel during the operationof a material feeder. Such an indication tends to eliminate the regularshutdowns and disassembly for measurement previously required.Furthermore, the apparatus and method provide an early warning of apending breakdown and indicate the right time for preventativemaintenance or barrel changeover. Thus, both a barrel and a feedscrewcan now be changed at the exact point in the operating life when theplasticizing rate drops off significantly. More than one measurementpoint can be provided with location and number of gage plug wearindicators determined by an analysis of the critical points in theparticular feeder.

There is shown in FIG. 9 a test bar 71 for calibrating the probe 115.The test bar 71 simulates a feedscrew and has a calibration section 72attached to a constant diameter section 73. The constant diametersection 73 can have the diameter of an unworn flight of the feedscrew tobe inspected. The calibration section 73 is formed with a plurality offlights that are stepped in diameter to simulate feedscrew wear. Forexample, the section 72 is formed with six flights 74 a through 74 fthat have a 6.75 inch lead. For the purposes of illustration, aplurality of planes 75 a through 75 l extends transverse to alongitudinal axis 76 of the test bar 71 at approximately one inchintervals. The test bar 71 can be formed of the same material as thefeedscrew. In addition, feedscrew flights typically are “hardfaced” byapplying a harder material to the surface to resist abrasion, such as a“Colmonoy 56” material available from Wall Colmonoy Corporation ofMadison Heights, Mich. Each of the flights 74 a through 74 f can be“hardfaced” with a different material to simulate actual feedscrewconstruction.

To the left of the plane 75 a, the constant diameter section 73 and theleft end of each of the flights 74 a through 74 f can have a diameter ofthree inches which simulates no wear. In the area between the planes 75a and 75 b, the flights can have a diameter of 2.990 inches whichsimulates a flight wear of 0.005 inches at diametrically opposed “sides”of the rest bar 71. In the area between the planes 75 b and 75 c, theflights can have a diameter of 2.980 inches which simulates a flightwear of 0.010 inches at diametrically opposed “sides” of the test bar71. The diameter of the flights can be reduced in a similar manner fromleft to right until the area to the right of the plane 75 l has adiameter of 2.880 inches which simulates a flight wear of 0.060 inchesat diametrically opposed “sides” of the test bar 71.

In operation, with the probe 115 installed in the measuring aperture 141and the test bar 71 inserted in the central bore 50 of the barrel 134,the test bar can be moved longitudinally to position a selected one ofthe areas of the calibration section 73 adjacent to the measuringaperture 141. Then, the test bar 71 is rotated to generate a signal fromthe probe 115 that corresponds to a known diameter of the test bar 71.

There is shown in FIGS. 10A and 10B an alternate embodiment gage plug157 having a cylindrical body 159 with a threaded recess 160 formed inan outer end surface for receiving a tool (not shown) to aid in removingthe gage plug 157 from an aperture in the feedscrew barrel wall. Thebody 159 has a top end portion 159 a with a hexagonal outer surfacesized for a standard open end wrench (not shown) of suitable size torotate the gage plug 157. At an inner end of the body 159 there isformed a radially extending flange 159 b having a shoulder 161 facingaway from the top end 159 a. A slot 159 c extends transverse to acentral axis of the body 159 at the opening of the recess 160 to receivea pin 172 (FIGS. 12A and 12B) that can be used when the gage plug 157 isinstalled in the feedscrew barrel to align the curvature of the plug endwith the curvature of the inner surface of the barrel. Extending axiallyinwardly from the flange 159 b is a plug outer section 163, a plugintermediate section 164 and a plug inner section 165. An inwardlyfacing end 166 of the inner section 165 is curved to correspond to thecurvature of the inner surface of the barrel and includes a cap 167formed of the same material as the liner or coating of the barrel.

There is shown in FIGS. 11A and 11B an alternate embodiment retainingplug 158 for holding the gage plug 157 in an aperture in the barrelwall. The retaining plug 158 has a cylindrical body 168 that isexternally threaded 169 at one end and has a top end portion 168 a witha hexagonal outer surface sized for a standard socket wrench (not shown)of suitable size for rotating the threads 169 into engagement withthreads in the aperture in the barrel wall. The body 168 has a throughaperture 170 extending along a central axis for receiving the centralportion of the gage plug body 159. The retaining plug 158 is threadedinto contact with the gage plug 157 to abut an end surface 168 b againstthe gage plug flange 159 b and seat the plug intermediate section 164against the aperture intermediate section 53.

The gage plug 157 and the retaining plug 158 are shown installed in thebarrel aperture 141 in FIGS. 12A and 12B. The gage plug 157 is insertedinto the aperture with the plug intermediate section 164 seated againstthe aperture intermediate Section 53. Then, the retaining plug 158 isthreaded into the aperture 141 to hold the gage plug 157 in place. Thepin 172 inserted in the slot 159 c is aligned with one or more of a markor alignment indicia 171 on the outer surface of the barrel 134 toposition the curved end 166 such that its curved surface blends with thecurved surface of the barrel inner surface 143. The pin 172 can be ofany suitable cross section, such as round, square, rectangular, etc.

There is shown in FIGS. 13A–G a mechanical version of the wear detectoraccording to the present invention. An adapter 180 (FIG. 13A) is shapedto be received in the aperture 141 just like the gage plug 157. A dialindicator 181 (FIG. 13B) is removably retained by the adapter 180 andhas a spherical radius nose piece 182 shaped to contact the flight 114of the feedscrew 111. The nose piece 182 is mounted on the end of anextension 183 removably attached to the shaft of the dial indicator 181.The dial indicator 181, the nose piece 182 and the extension 183 are allconventional, commercially available items. Typically, the shaft of thedial indicator 181 can be approximately one inch long and the extension183 can be approximately two inches long.

A calibration and measuring fixture 184 (FIG. 13C) has a firstupstanding leg 185 that removably retains the dial indicator 181 in ahorizontal position (FIG. 13D) with the shaft extending toward a secondupstanding leg 186. The second leg 186 has a stepped cylindricalaperture 187 formed therein for receiving the gage plug 157. Acalibration standard 188 (FIG. 13E) also fits into the aperture 187 andis releasably held by a retainer 188 a (FIG. 13D).

The calibration standard 188 is used with the fixture 184 to establish alocation for the dial indicator 181, without the extension 183, so thatsubsequent readings will be meaningful (FIG. 13D). Prior to taking eachmeasurement, the dial indicator 181 is “zeroed” using the calibrationstandard 188. Then, the current measurement of the gage plug 157 can becompared with previous measurements to determine the amount and the rateof wear of the barrel 134.

Screw wear measurements are made using the dial indicator 181 with theextension 183 and the adapter 180. After the dial indicator 181 with theextension 183 is mounted in the adapter 180, the shaft of the dialindicator is “zeroed” to the end of the adapter. This can be doneagainst any flat surface. Then, the assembly is placed in the aperture141 (FIG. 13F) to obtain a reading from the flight 114 of the feedscrew111 (FIG. 13G). Then, the current measurement of the flight 114 can becompared with previous measurements to determine the amount and the rateof wear of the feedscrew 111.

Prior to the wear detector according to the present invention, theextruder was cooled to room temperature and disassembled in ordermeasure the barrel interior and the feedscrew for wear. The mechanicalversion of the wear detector has the advantage that it can be usedbefore the extruder has completely cooled down and without anydisassembly other than to remove the gage plug. Any number of the gageplugs can be used, but the metering section is most critical for optimumperformance of the extruder and the transition section tends to have themost wear.

There is shown in FIGS. 14A–C an alternate embodiment barrel apertureand gage plug. As shown in FIG. 14A, an aperture 241 is similar to theaperture 141 (FIG. 6), but includes a pin or dowel 262 mounted in thebarrel wall and extending parallel to the aperture axis 56. As shown inFIGS. 14B and 14C, a gage plug 257, similar to the gage plug 157 (FIGS.10A–10B), has a body 259 with a radially extending flange 259 b near aninner end of the body. The flange has a peripheral groove 259 dextending parallel to the aperture axis 56 for receiving the dowel 262to align the curved inner end of the plug 257 to correspond to thecurvature of the inner surface of the barrel 134. An externally threadedportion 259 e of the body 259 is positioned between the outer end andthe flange 259 b. The retaining plug 158 (FIGS. 11A–11B) can be usedwith the gage plug 257.

The gage plug 257 is removed from the barrel aperture 241 utilizing anextractor kit 290 shown in FIGS. 14D and 14E. The kit 290 includes anextractor rod 291, an extractor V-block 292 and an extractor nut 293.The rod 291 has an internally threaded axially extending aperture 294formed at an inner end for threadably engaging the externally threadedportion 259 e of the body 259. Thus, the retaining plug 158 is removedand the rod 291 is threaded into engagement with the gage plug 257 inthe aperture 241. The V-block 292 is generally rectangular incross-section and has a generally V-shaped inner surface 295 forcontacting the curved outer surface 142 (FIG. 14A) of the barrel 134. Acentral aperture 296 is formed through the V-block 292 between the innersurface 295 and an outer surface. The aperture 296 is sized to slidablyreceive the rod 291. The rod 291 has a threaded external surface 297that extends beyond the V-block 292 and is threadably engaged by the nut293 to contact the V-block 292 which is contacting the barrel 134. Asthe nut 293 is rotated in an engaging direction, a withdrawing force isapplied to the rod 291 to remove the gage plug 257 from the aperture241.

In any of the above-described embodiments, when the gage plug is removedfrom the barrel aperture, molten material can flow into the barrelaperture and harden in the threaded wall. This excess material must becleaned from the aperture before the gage plug can be reinstalled. Thus,a cleaning plug, similar to the retaining plugs 58 and 158, can beformed from a softer material, such as brass, and threaded into theaperture 141, 241 to clean the threads without damaging them.

There is shown in FIG. 15 a system 300 according to the presentinvention for monitoring and maintaining production installations. Aproduction installation “A” 301 includes one or more machines having abarrel and a feedscrew to be monitored. A monitoring apparatus 302,according to at least one of the embodiments described above, provideswear data and related information to a data collection and storage means303. The related information can include such data as the material beingprocessed, the speed of rotation of the feedscrew and the temperaturesbeing generated in the barrel. The stored data can be transmitted by adata transmission means 304 to a central data receiving means 305. Acomputer program can be provided in the data analysis means 306 for usewith the wear detectors according to the present invention. The programcan calculate, graph and display the wear data to show information, suchas amount of wear and the wear rate. Thus, the optimum time forreplacing the feedscrew and/or the barrel can be predicted.

The wear data is analyzed by a data analysis means 306 to provide rateof wear information and predictions of the remaining life of each of thebarrel and the feedscrew of the production machine. The wear informationand life predictions then can be sent to the installation “A” 301 by aninstallation notification means 307.

The wear information and life predictions also can be used by a partsorder generation means 308 to start the manufacture of replacement partsso that they will be ready to ship to the installation and install whenthe production machine wears out. The specifications for each barrel andfeedscrew can be transmitted by the installation with the other data, orstored in the data analysis means 306 at some prior time. In thismanner, the machine down time can be kept to a minimum. Of coursemultiple installations can be monitored by the data receiving means 305as shown by an installation “B” 309 and an installation “X” 310.Although not shown, each of the installations 309 and 310 are connectedto the data receiving means 305 by means similar to the means 302, 303and 304. Typically, the means 303 and 304 are implemented in a computerthat is connected to the computer of the data receiving means 305 by asecure link over telephone lines, the Internet, etc.

The monitoring apparatus 302 can take forms other than the gage plugsand measuring devices described above. For example, the barrel wear canbe monitored using ultrasound measurement. In that case, the monitoringapparatus 302 can include an ultrasonic thickness gauge, such as model“DMS 2” available from Krautkramer Branson of Lewistown, Pa. This devicegenerates output data on a visual display and in electronic formatsuitable for transmission to a computer. Other suitable ultrasonicthickness gauges available from Krautkramer are the models “DM4” and“DM4 DL”. The monitoring apparatus 302 can include an eddy currentdevice, as shown in the U.S. Pat. No. 4,604.251, for monitoring thefeedscrew wear.

In accordance with the provisions of the patent statutes, the presentinvention has been described in what is considered to represent itspreferred embodiment. However, it should be noted that the invention canbe practiced otherwise than as specifically illustrated and describedwithout departing from its spirit or scope.

1. An apparatus for determining wear of a feedscrew and barrelcombination comprising: a barrel having a central bore extending along alongitudinal axis and a measuring aperture formed in a wall of saidbarrel, said measuring aperture extending along an axis radially fromsaid longitudinal axis; a feedscrew rotatably positioned in said centralbore; a gage plug releasably retained in said measuring aperture, saidgage plug having an inner end curved to correspond to a curvature of asurface of said central bore surrounding an inner end of said measuringaperture; and measuring means for determining barrel wear at said gageplug inner end when said gage plug is removed from said measuringaperture and for determining wear of said feedscrew upon being insertedinto said measuring aperture.
 2. The apparatus according to claim 1wherein said measuring means includes a dial indicator and a fixture,said fixture holding said gage plug and said dial indicator in apredetermined relationship for measuring said barrel wear.
 3. Theapparatus according to claim 2 including a calibration standard for usewith said fixture to “zero” said dial indicator.
 4. The apparatusaccording to claim 1 wherein said measuring means includes a dialindicator and an adapter received in said measuring aperture formeasuring said wear of said feedscrew.
 5. The apparatus according toclaim 4 including an extension attached to said dial indicator andextending through said adapter.
 6. The apparatus according to claim 1including an extractor kit for removing said gage plug from saidmeasuring aperture.
 7. The apparatus according to claim 6 wherein saidextractor kit includes an externally threaded extractor rod having athreaded aperture for threadably engaging said gage plug, an extractorV-block for contacting an external surface of said barrel, saidextractor rod passing through said V-block, and an extractor nutthreadably engaging said extractor rod whereby rotation of saidextractor nut pulls said extractor rod and said gage plug from saidmeasuring aperture.
 8. The apparatus according to claim 1 including anaxially extending dowel attached to said barrel wall in said measuringaperture and wherein said gage plug has a groove formed therein, saidgroove cooperating with said dowel to orient said gage plug in saidmeasuring aperture.
 9. A method for monitoring wear of a feedscrew andbarrel combination in a production installation comprising the steps of:a. providing a measuring aperture in a wall of a barrel having a centralbore extending along a longitudinal axis, the measuring apertureextending along an axis radially from the longitudinal axis; b.positioning a feedscrew rotatably in the central bore; c. installing aplug releasably retained in the measuring aperture, the plug having aninner end curved to correspond to a curvature of a surface of thecentral bore surrounding an inner end of the measuring aperture; d.measuring barrel wear with at least one of the plug and a firstmeasuring device; and e. measuring feedscrew wear with at least one ofthe plug and a second measuring device.
 10. The method according toclaim 9 wherein the plug is a gage plug, the first measuring deviceincludes a dial indicator and a fixture and said step d. is performed bymounting the gage plug and the dial indicator in the fixture.
 11. Themethod according to claim 9 wherein the first measuring device includesan ultrasonic thickness gauge and said step d. is performed by using theultrasonic thickness gauge at an external surface of the barrel.
 12. Themethod according to claim 9 wherein the second measuring device includesa dial indicator and said step e. is performed by removing the plug andmounting the dial indicator in the measuring aperture.
 13. The methodaccording to claim 9 wherein the plug is an eddy current sensor, thesecond measuring device includes a detection signal circuit and saidstep e. is performed by rotating the feedscrew.
 14. A method formonitoring wear of a feedscrew and barrel combination in a productioninstallation comprising the steps of: a. measuring at least one ofbarrel wear and feedscrew wear; b. generating wear data from themeasured wear; c. transmitting the wear data to a remote location; d.analyzing the wear data at the remote location; and e. predicting aremaining life of the barrel and/or the feedscrew based at leastpartially upon the analyzed wear data.
 15. The method according to claim14 including a step of generating an order for the manufacture andshipment to the production installation of the barrel and/or thefeedscrew to coincide with an end of the predicted remaining life. 16.The method according to claim 14 including performing said step c. bytransmitting at least one of a material being processed, a speed ofrotation of the feedscrew and an operating temperature of the barrel.17. The method according to claim 14 including transmitting the analyzedwear data from the remote location to the production installation. 18.The method according to claim 14 including performing said steps a.through e. for at least two physically separated productioninstallations.